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Closed Access item Expanding the realm of ultrafast protein folding: gpW, a midsize natural single-domain with α+β topology that folds downhill

Authors:Fung, Adam
Li, Peng
Godoy-Ruiz, Raquel
Sánchez-Ruiz, José M.
Muñoz van den Eynde, Víctor
Keywords:Protein folding, Ultrafast folding proteins, gpW, Thermodynamic analysis, Downhill folding, Folding barriers
Issue Date:14-May-2008
Publisher:American Chemical Society
Citation:Journal of the American Chemical Society 130(23): 7489-7495 (2008)
Abstract:All ultrafast folding proteins known to date are either very small in size (less than 45 residues), have an α-helix bundle topology, or have been artificially engineered. In fact, many of them share two or even all three features. Here we show that gpW, a natural 62-residue α+β protein expected to fold slowly in a two-state fashion, folds in microseconds (i.e., from τ = 33 µs at 310 K to τ = 1.7 µs at 355 K). Thermodynamic analyses of gpW reveal probe dependent thermal denaturation, complex coupling between two denaturing agents, and differential scanning calorimetry (DSC) thermogram characteristic of folding over a negligible thermodynamic folding barrier. The free energy surface analysis of gpW folding kinetics also produces a marginal folding barrier of about thermal energy (RT) at the denaturation midpoint. From these results we conclude that gpW folds in the downhill regime and is close to the global downhill limit. This protein seems to be poised toward downhill folding by a loosely packed hydrophobic core with low aromatic content, large stabilizing contributions from local interactions, and abundance of positive charges on the native surface. These special features, together with a complex functional role in bacteriophage λ assembly, suggest that gpW has been engineered to fold downhill by natural selection.
Description:7 pages, 5 figures.-- PMID: 18479088 [PubMed].-- Printed version published on Jun 11, 2008.
Publisher version (URL):http://dx.doi.org/10.1021/ja801401a
URI:http://hdl.handle.net/10261/9346
ISSN:0002-7863
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